The disclosed invention relates generally to a voltage level shifter, and in particular, to a voltage level shifter having a single-rail input.
The need to reduce on-chip power consumption has continued to increase as the number of transistors within chips (e.g., microprocessor, graphics chips) increases and as electronic devices that use these chips are scaled down, for example, for greater mobility. Historically, the low power consumption targets of chips have been achieved by aggressively scaling down their power supply voltages.
In an effort to further reduce overall power consumption, many chip designs also include two or more different power supply domains. Non-critical blocks within a chip, for example, can be designed to consume minimal amounts of energy by tying them to lower power supply voltages in a low power supply domain. Within the same chip, timing critical blocks that require the stability associated with a high power domain can be designed to use higher power supply voltages. Often voltage level shifters are used to convert voltages in the high power supply domain to voltages in the low power supply domain.
Known voltage level shifters, unfortunately, have several drawbacks. For example, known voltage level shifters can consume high levels of power at certain corners of operation. Also, some known voltage level shifter designs can include dual-rail inputs and/or additional inverters that not only require excessive chip real-estate, but also consume additional power. Accordingly, a need exists for improved methods and apparatus for converting power supply voltages from one voltage domain to a different voltage domain.